If there’s one date range every Medicare beneficiary should have marked on their calendar, it’s the Annual Enrollment Period (AEP). This is the main window each year when you can review, switch, or update your Medicare coverage — and missing it can mean waiting a full year for another chance. Here’s everything you need to know.
What Is the Medicare Annual Enrollment Period?
The Annual Enrollment Period, sometimes called the Fall Open Enrollment Period, runs every year from October 15 to December 7. During this window, anyone with Medicare can make changes to their coverage, regardless of their current plan or health status.
Any changes made during AEP take effect on January 1 of the following year.
What Can You Change During AEP?
The Annual Enrollment Period is the most flexible window of the year — you can make any of the following changes:
- Switch from Original Medicare to a Medicare Advantage plan
- Switch from a Medicare Advantage plan back to Original Medicare
- Switch from one Medicare Advantage plan to a different one
- Switch from one Part D prescription drug plan to another
- Join a Part D plan for the first time, if you didn’t enroll when first eligible
- Drop a Part D plan entirely, if you no longer want prescription drug coverage
This makes AEP the only time of year when you have complete freedom to reconsider your entire Medicare setup, not just make a single, limited adjustment.
Why AEP Matters So Much
Plans change every year — premiums, covered drugs, provider networks, and extra benefits can all shift from one year to the next, even if you don’t do anything. This is why reviewing your coverage annually during AEP is strongly recommended, even if you were happy with your plan the previous year. A plan that was a great fit last year may look very different for the year ahead.
Insurance companies are required to send an Annual Notice of Change (ANOC) to current enrollees each September, outlining exactly what will change about their plan for the upcoming year. Reading this notice carefully is one of the most useful (and most skipped) steps in the entire process.
Step-by-Step: How to Use AEP Effectively
- Review your ANOC letter (arrives in September) to understand what’s changing about your current plan.
- Reassess your health needs — has anything changed in the past year? New medications, new diagnoses, or a preferred provider that’s changed?
- Compare plans available in your area using Medicare’s official Plan Finder tool or by speaking with a licensed agent.
- Check that your doctors and pharmacies are in-network for any plan you’re considering switching to.
- Confirm your medications are covered under the plan’s drug formulary, and check the specific tier/cost for each.
- Make your decision and enroll before December 7 to ensure your new coverage takes effect January 1.
What Happens If You Don’t Make Any Changes?
If you’re satisfied with your current plan, you don’t need to do anything during AEP — your coverage will automatically continue into the new year, subject to whatever changes were outlined in your ANOC letter. However, «doing nothing» should still be an active choice after reviewing your notice, not a default by omission — plans can quietly become less favorable year over year if you’re not paying attention.
AEP vs Other Enrollment Periods: Don’t Get Them Confused
This is one of the most common points of confusion, so here’s a quick clarification:
| Enrollment Period | When | What You Can Do |
|---|---|---|
| Annual Enrollment Period (AEP) | Oct 15 – Dec 7 | Full flexibility — switch any Medicare coverage |
| Medicare Advantage Open Enrollment Period | Jan 1 – Mar 31 | One plan change, only if already on Medicare Advantage |
| Initial Enrollment Period | Around your 65th birthday | First-time enrollment in Medicare |
| Special Enrollment Period | Triggered by specific life events | Limited changes tied to the qualifying event |
We cover the Medicare Advantage Open Enrollment Period and Special Enrollment Periods in more detail in their own dedicated guides, since each has different rules about what changes are actually allowed.
Common Mistakes People Make During AEP
- Not reading the ANOC letter, and missing important changes to premiums, drug coverage, or provider networks.
- Assuming last year’s plan is still the best option, without comparing it against newer plans available in the same area.
- Waiting until the last few days, which limits time to properly research options or speak with an agent.
- Not checking whether specific medications are still covered, which can lead to unexpectedly high prescription costs the following year.
- Overlooking extra benefits (dental, vision, hearing) that may have changed or been added to new plans in your area.
When Should You Start Preparing for AEP?
Most Medicare experts recommend starting your research in September, as soon as ANOC letters go out, rather than waiting until October 15. This gives you several extra weeks to compare plans calmly, rather than rushing through the process in the final days before December 7.
Frequently Asked Questions
Can I switch Medicare Advantage plans more than once during AEP? Yes — during AEP itself, you can make as many changes as you want; only your final selection by December 7 will take effect.
Does AEP apply to Medigap policies too? No — Medigap enrollment and underwriting rules are separate from AEP and follow different timing, generally tied to your Original Medicare enrollment date.
What happens if I miss the December 7 deadline? You’ll generally need to wait until the next AEP the following year, unless you qualify for a Special Enrollment Period due to a specific life event.
Is there a cost to switch plans during AEP? No — there’s no fee to compare or switch plans during AEP itself, though your new plan’s premiums and costs may differ from your previous plan.
What’s Next
Now that you understand how AEP works, here’s what to explore next:
- [How to Compare Medicare Advantage Plans Before Enrolling] — a practical checklist to use during your research.
- [Medicare Advantage Open Enrollment Period: What You Can Change] — understand your options if you miss AEP or want to make a later adjustment.
- [Medicare Advantage Late Enrollment Penalty: How Much It Costs] — understand the cost of delaying enrollment altogether.